1. Field of the Invention
The present invention relates to time locks for bank vaults and, more particularly, to a low current drain battery operable timer for releasing a gravity operated mechanical block.
2. Description of the Prior Art
For decades, mechanical timers have been employed as time locks for bank vaults. Such mechanical timers must be accurate despite environmental changes and wear. To eliminate wear as a variable, substantial maintenance has been required. The setting of mechanical time locks is generally complicated and missetting often occurs.
Various electrically operated time locks can be used but the power consumption is relatively high. With high power consumption, battery power becomes a predominant problem for long term settings. Reliance upon a source of alternating current from conventional power sources or backup generators will not satisfy criteria for good practice.
Electromechanical time locks for bank vaults generally suffer from all of the wear and maintenance problems attendant mechanical locks and generally have high power requirements. While the electrical timers in electromechanical locks are generally sufficiently accurate, the mechanics activated to lock and unlock a bank vault require high tolerances subject to malfunction due to contamination or are easily detuned to the state of inoperability and require meticulous adjustments.